Electronic expansion valves having multiple orifice plates
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Solution Overview
Problem
Existing expansion devices for refrigeration and heat pump systems, particularly small systems, face challenges in controlling refrigerant flow rates over a wide range of operating conditions due to high manufacturing costs, reliability issues, and inefficiencies at off-design conditions, especially with small orifices and valve-seats prone to blockages, and slow reaction times.
Innovation Solution
An electronic expansion valve assembly with a motor-driven linear-drive assembly and multiple orifice plates arranged in series, allowing for adjustable needle position and increased pressure loss across the valve, enabling robust control of refrigerant flow over a wide range of conditions without increasing physical size, thus managing flow rates effectively at low mass flow rates and varying differential pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single fixed orifice is used in thermal expansion valves, then the valve is low cost and simple in structure, but it provides non-controlled performance at off-design conditions and has slow reaction time
Solution Approach 1:
The single orifice is segmented into multiple orifices arranged in series. This allows the expansion valve to provide controlled performance across a wider range of operating conditions while maintaining a relatively simple and cost-effective structure. The multiple orifices enable better flow regulation at off-design conditions compared to a single fixed orifice.
2Stress or pressure
If small orifices and valve-seats are used to achieve high flow restriction, then the pressure drop is sufficient, but they are prone to blockages due to debris
Solution Approach 1:
The flow restriction is segmented across multiple orifices in series rather than concentrated in a single small orifice. This distribution reduces the susceptibility to blockages while maintaining the necessary pressure drop across the valve.
Solution Approach 2:
Different orifices in the series can have different sizes and characteristics, allowing optimization of each orifice for specific functions. This enables the system to achieve high pressure drop without requiring all orifices to be small, thereby reducing blockage risk.
3Manufacturing precision
If a tapered needle with tight tolerances is used to achieve repeatable performance, then the manufacturing precision is high, but the manufacturing cost increases
Solution Approach 1:
The flow control function is segmented across multiple orifices rather than relying on a single tapered needle with tight tolerances. This approach achieves repeatable performance through the collective effect of multiple orifices, reducing the manufacturing precision requirements for individual components and lowering overall manufacturing cost.
4Quantity of substance
If the refrigerant flow rate is very low in small systems, then the physical dimensions of the needle-orifice must be very small, but this makes manufacturing difficult and requires very tight tolerances
Solution Approach 1:
The flow control for low refrigerant flow rates is achieved by segmenting the orifice structure into multiple smaller orifices in series. This allows the use of larger, more manufacturable components while still achieving the necessary flow restriction, thereby reducing tolerance requirements and manufacturing difficulty.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides reliable, cost-effective control of refrigerant flow with a wider operating range and higher pressure loss for a given flow rate, reducing manufacturing costs and minimizing blockages, while ensuring consistent performance across varying conditions.
Implementation Method 1
a motor-driven linear-drive assembly configured to move the needle along a needle extension pathway through the valve body
Implementation Method 2
Expansion devices are used to regulate and control the flow of a fluid from a high pressure to a low pressure... providing a higher pressure loss for a given flow rate than a valve that utilizes only a single orifice
Data Source
AI summary
An electronic expansion valve (EEV) is operated by a motor controlling a variable restriction valve in which a liquid refrigerant enters at a high pressure and exits at a reduced pressure. The motor controls the depth of a tapered needle which, as extended, penetrates multiple fixed orifices, aligned in series. Additional fixed orifices, downstream of the fully extended needle, provide further restriction and management of refrigerant flashing. Depending on the desired operating range, the following elements may be controlled: needle length, diameter, and taper; diameter, thickness, and relative elevation of each orifice; response and maximum torque provided by the motor; and geometry of the valve enclosed volume.